Conventionally the development of motor-driven valves having a smaller size, larger capacity and more energy efficient has been promoted. As one example of such a conventional motor-driven valve, a technology is disclosed at JP 2013-130271A, making it possible to include a valve opening spring with a small spring load by minimizing the force acting in the valve-closing direction.
The motor-driven valve disclosed in JP 2013-130271A includes: a valve body having a valve chamber, a horizontal first inlet-outlet port that opens on the valve chamber, a vertical valve port with a valve seat that opens on the valve chamber, and a second input-outlet port connected to the valve port; a valve element that is disposed in the valve chamber in a vertically ascendable/descendable manner so as to open/close the valve port; vertically driving means having an electric motor to make the valve element ascend/descend; and a valve opening spring to bias the valve element in the valve opening direction. The diameter of the valve port and the diameter of a back pressure chamber defined above the valve element are substantially the same, a pressure equalizing path is provided in the valve element, having a lower end face that opens so as to allow the valve port and the back pressure chamber to communicate, and the components of the valve have dimensions so that the value obtained by dividing the area of the lower end opening of the pressure equalizing path by the area of the valve port is within a predetermined range.
In this type of motor-driven valves, fluid (refrigerant) flows in two directions including a first flowing direction from the first inlet-outlet port to the second inlet-outlet port and a second flowing direction from the second inlet-outlet port to the first inlet-outlet port. If refrigerant as gas (gas refrigerant) flows in the first flowing direction in a gas-excessive state, for example, there is a problem that a periodical vortex flow occurs in the vicinity of the region between the lateral part of the valve port and the inner wall face of the valve body when the valve chamber is viewed from the first inlet-outlet port, and noise is generated accordingly. If refrigerant flows in the second flowing direction in a gas-excessive state, for example, there is a problem that a periodical vortex flow occurs in the vicinity of the region between the part of the valve port on the opposite side of the first inlet-outlet port and the inner wall face of the valve body (especially in a region close to the valve port in that region), and noise is generated accordingly (see FIG. 4). Specifically, the experiment by the present inventors showed that, if refrigerant flows in the first flowing direction in a gas-excessive state, the above-mentioned periodical vortex flow occurs at a high differential pressure and with a very small opening degree of the valve (see FIG. 5).
Conventionally such noise during operation has been a concern for various types of valve devices, and so JP H09-310939A and JP 2002-235969A disclose prior art to suppress noise of an expansion valve or a dry valve used in a refrigerating cycle.
The expansion valve disclosed in JP H09-310939A includes a valve body having openings at the lateral face and the lower face as well as a space inside, a valve element and a valve seat defining a throttle inside of the valve body, a shaft coupled with the valve body and having a rotor at an upper part thereof, a case surrounding the shaft and the rotor, a stator located at the outer circumference of the rotor, supporting means that supports the valve element and the shaft, and a first pipe connected to the opening at the lateral face of the valve body and a second pipe connected to the opening at the lower face of the valve body. Such an expansion valve includes a hollow rectifier located inside of the valve body that has one end fixed to the valve body and the other end fixed to the supporting means, and has a plurality of through holes at the lateral face thereof.
The dry valve disclosed in JP 2002-235969A is provided with a path around the valve seat so as to allow a valve chamber and a valve outlet port to communicate when the valve is closed, and includes a throttle made of a porous body in this path and an elastic member located close to a valve stem of the dry valve so that the elastic member comes into contact with the porous body when the valve is closed, wherein this elastic member functions as a valve element and this porous body functions as a valve seat.
The prior art disclosed in JP H09-310939A, however, has the following problems. That is, refrigerant flowing into through the first pipe comes around the space defined by the valve body and the rectifier, flows into the space storing the valve element through the plurality of through holes formed at the rectifier, and passes through the throttle defined by the valve element and the valve seat to flow into the second pipe. Therefore although noise can be reduced by suppressing vibrations of the valve element and the case due to fluctuations in pressure caused by the non-uniform state of the refrigerant, other problems occur, such as an increase in flow rate loss of the refrigerant or the complicated arrangement and configuration of the rectifier.
The prior art disclosed in JP 2002-235969A has the following problems. This technique has the effect of reducing discontinuous sound and so lead to the sound deadening effect because the refrigerant is rectified when it passes through the porous body and even when a gas-liquid two-phase flow generating the sound of refrigerant flow the most remarkably flows, this gas-liquid two-phase flow is homogenized and the pressure is reduced in this homogenized state. However, other problems occur, such as a large flow rate loss of the refrigerant and the necessity for the porous body to function as a valve seat.